There was a day when GOP leaders agreed that all Americans should have coverage, as in every other advanced nation on earth.

If you look at the politics surrounding President Obama’s health care reform, the Republican strategy in this year’s elections seems promising. The law remains unpopular, with recent polls showing an average 12.5 percent gap between supporters and opponents, according to RealClearPolitics.

So Republicans will win votes by tapping into that discontent, even if a good piece of the opposition is based on concern over nonexistent death panels and other nonsense. The constant vilification of this reform has made its mark.

But if you look at the law’s impact on the ground, the results are impressive. A Gallup poll released this week indicated that 12 million previously uninsured Americans have gained coverage since last fall, even after subtracting those who lost coverage when the law took effect because their plans were substandard.

The 12 million include people who gained coverage on their own, so Obamacare can’t claim full credit. But so far, 8 million had signed up for private plans on the exchanges, and more than 3 million had signed up for Medicaid.

Not surprisingly, progress has been lopsided. States that embraced the reform by accepting the Medicaid expansion and setting up their own exchanges saw their uninsured rate drop three times as fast as it did in other states. As of this month, the rate in supportive states was 13.6 percent, compared to 17.9 percent in states that rejected these measures.

What we are witnessing is the formation of another deep fissure between red and blue states, this time on health care. Republicans on the whole oppose the law by a margin of 6-1. And in red states, Republican governors and legislatures are doing all they can to keep it that way by sabotaging the law’s effectiveness.

Democrats support the law by a 3-1 margin, Gallup has found. And in blue states that are cooperating with the reform, it is working much better. In those states, the rate of uninsured is dropping three times as fast.

New Jersey is a hybrid because Gov. Chris Christie agreed to expand Medicaid, but did not set up a state exchange and so we missed out on federal money for outreach.

The political reality is that Obama and the Democrats have at least two years to build on this progress before Republicans have a shot in 2016 to take the White House and Senate. Even then, would they really pull the trigger? The 12 million figure will have doubled or tripled by then. What will Republicans tell that army of people to do when they pull the rug out?

To watch the evolution of the Republican Party on this issue has been nothing but sad. There was a day when GOP leaders agreed that all Americans should have coverage, as in every other advanced nation on Earth. The argument was about how to achieve that goal. Progressive Democrats wanted a single-payer system based on Canada’s.

Republicans instead gave us Romneycare in Massachusetts, and Obama embraced that model as a compromise.

His reward has been unrelenting hostility from Republicans, who gave us deliberate distortions such as the infamous “death panels” during the debate, and who now are attempting to sabotage its effectiveness. They have no plausible plan to achieve universal coverage, or anything near it. They have no credible plan B. And in the end, that fact could doom their efforts to repeal Obamacare.